Published in Journal of Solid State Chemistry 177, issue 8, 2841-2849, 2004 1 which should be used for any reference to this work Synthesis, structure and magnetic properties of cobalt(II) and copper(II) coordination polymers assembled by phthalate and 4-methylimidazole Svetlana G. Baca,a,* Stanislav T. Malinovskii,a Patrick Franz,b Christina Ambrus,b Helen Stoeckli-Evans,c Nicolae Gerbeleu,a and Silvio Decurtinsb a Institute of Chemistry, Academy of Sciences of R. Moldova, Academiei 3, MD-2028 Chisinau, Moldova b Department of Chemistry and Biochemistry, University of Berne, CH-3012 Berne, Switzerland c Institut de Chimie, Universite` de Neuchaˆtel, CH-2007 Neuchaˆtel, Switzerland Abstract 2À New coordination polymers [M(Pht)(4-MeIm)2(H2O)]n (M=Co (1), Cu (2); Pht =dianion of o-phthalic acid; 4-MeIm=4- methylimidazole) have been synthesized and characterized by IR spectroscopy, X-ray crystallography, thermogravimetric analysis and magnetic measurements. The crystal structures of 1 and 2 are isostructural and consist of [M(4-MeIm)2(H2O)] building units linked in infinite 1D helical chains by 1,6-bridging phthalate ions which also act as chelating ligands through two O atoms from one carboxylate groupin the case of 1. In complex 1, each Co(II) atom adopts a distorted octahedral N2O4 geometry being coordinated by two N atoms from two 4-MeIm, three O atoms of two phthalate residues and one O atom of a water molecule, whereas the square-pyramidal N2O3 coordination of the Cu(II) atom in 2 includes two N atoms of N-containing ligands, two O atoms of two carboxylate groups from different Pht, and a water molecule. An additional strong O–H?O hydrogen bond between a carboxylate groupof the phthalate ligand and a coordinated water molecule join the 1D helical chains to form a 2D network in both compounds. The thermal dependences of the magnetic susceptibilities of the polymeric helical Co(II) chain compound 1 were simulated within the temperature range 20–300 K as a single ion case, whereas for the Cu(II) compound 2, the simulations between 25 and 300 K, were made for a linear chain using the Bonner–Fisher approximation. Modelling the experimental data of compound 1 with MAGPACK resulted in: g ¼ 2:6; |D|=62 cmÀ1. Calculations using the Bonner–Fisher approximation gave the following result for compound 2: g ¼ 2:18; J ¼ 20:4cmÀ1. Keywords: Phthalate compounds; Carboxylate complexes; Dicarboxylic acid; Cobalt(II); Copper(II); Coordination polymer; Crystal structure; Helical chain; Magnetic properties 1. Introduction tures, but also due to their advantageous properties such as bulk magnetic behavior, high dimensionality, optical Inorganic coordination polymers or solid-state poly- activity and thermal stability. In particular, coordina- mers have received considerable attention in the past few tion polymers with terephthalic [2], isophthalic [3] and years due to possible applications as new materials in phthalic acids [4–31] have been extensively studied. catalysis, adsorption, ion exchange, separation, mag- Among these isomeric forms the o-phthalate ligand, netic devices, etc. (for recent reviews see [1]). Metal with two carboxylic groups in ortho-position, can adopt coordination polymers containing dicarboxylate ions as the most diverse bonding modes (26 coordination modes the organic spacer have been the subject of particular [32]) in metal complexes. As a result, it can be expected interest not only because of their fascinating architec- that more complicated and unexpected architectures leading to new properties and reactivity can be *Corresponding author. Fax: +373-22-73-9611. constructed. We have recently become interested in the E-mail address: sbaca [email protected] (S.G. Baca). synthesis of 3d-coordination compounds with the 2 phthalate and N-containing ligands. Copper(II) [32–33], 817m, 767m, 722m, 701w, 657s, 621m, 561w. Single cobalt(II) [32,34], and zinc(II) [32,35–36] coordination crystals suitable for diffraction studies were obtained by polymers have been reported so far. In an extension of recrystallization of 2 from hot aqueous solution. the study here we report on the synthesis, crystal structure and magnetic properties of new cobalt(II) 2.3. Crystal structure determination and copper(II) mixed-ligand coordination polymers 2À [M(Pht)(4-MeIm)2(H2O)]n (where Pht =dianion of Single crystal X-ray diffraction data for 1 and 2 were o-phthalic acid, 4-MeIm=4-methylimidazole). collected on a Stoe Mark II—Imaging Plate Diffract- ometer System [37] equipped with a two-circle goni- ometer and using MoKa graphite-monochromated 2. Experimental radiation at 153 K. Image plate distance 100 mm, o rotation scans 0–180 at f 0, and 0–35 at 90, step 2.1. Materials and methods Do ¼ 1:2 ; 2y range 2.29–59.53 , dmax–dmin=17.799– 0.716 A˚ . The crystallographic data and details on the All the starting materials were reagent grade and used refinements for 1 and 2 are summarized in Table 1. The as purchased. The infrared spectra were recorded on a structures were solved by direct methods using the Perkin–Elmer Spectrum One spectrometer using KBr programme SHELXS-97 [38]. The refinement and all pellets in the region 4000–400 cmÀ1. Thermogravimetric further calculations were carried out using SHELXL-97 analyses were carried out in dry nitrogen (60 mL/min) at [39]. The H-atoms were located from Fourier difference a heating rate of 5C/min from room temperature (r.t.) maps and refined isotropically. The water molecule H- to 600C on a Mettler-Toledo TA 50 instrument. atoms were also located from difference maps but were ˚ 2 held fixed with Uiso=1.5(Ueq–O–atom) A . The non-H 2.2. Synthesis atoms were refined anisotropically, using weighted full- matrix least squares on F2. Selected bond lengths and 2.2.1. [Co(Pht)(4-MeIm)2(H2O)]n (1) angles for 1 and 2 are listed in Table 2. Crystallographic A solution of Co(O2CMe)2 Á 4H2O (1.24 g, 5 mmol) in data for the structural analysis have been deposited with water (10 mL) was added to a hot solution of KHPht the Cambridge Crystallographic Data Centre, CCDC (1.02 g, 5 mmol) and 4-MeIm (0.82 g, 10 mmol) in water nos. 234706 (1), 234707 (2). Copies of this information (10 mL). The resulting mixture was stirred and heated may be obtained from The Director, CCDC, 12 Union for 30 min and left to stand overnight at r.t. The dark Road, Cambridge, CB2 1EZ, UK (fax: +44-1233- red crystalline product was filtered off, washed with 336033; e-mail: [email protected] or www: water and ethanol and dried in air. Yield: 1 g, 50%. An http://www.ccdc.cam.ac.uk). additional batch of 1 can be obtained by keeping the mother filtrate in air over 2 weeks (yield ca. 20%). Anal. 2.4. Magnetic measurements Calc. for C16H18CoN4O5: C, 47.42%; H, 4.48%; N, 13.82%. Found: C, 47.94%; H, 4.54%; N, 13.81%. IR Magnetic susceptibility data of powdered samples data (KBr, cmÀ1): 3414s,br, 3211s, 3008sh, 1596sh, were collected on a MPMS Quantum Design SQUID 1559vs,br, 1493s, 1446s, 1417vs, 1396vs, 1259w, 1234w, magnetometer (XL-5) in the temperature range of 300– 1158w, 1108m, 1088w, 962m, 870sh, 840m, 816m, 770m, 1.8 K and at a field of 1000 G. The samples were placed 725m, 701m, 662s, 624w, 584m. Single crystals suitable in a gelatine capsule and a straw was used as the sample for diffraction studies were obtained by recrystallization holder. The output data were corrected for the of 1 from hot aqueous solution. experimentally determined diamagnetism of the sample holder and the diamagnetism of the sample calculated 2.2.2. [Cu(Pht)(4-MeIm)2(H2O)]n (2) from Pascal’s constants. The Levenberg–Marquardt A solution of Cu(O2CMe)2 Á H2O (1 g, 5 mmol) in least-squares fitting algorithm, in combination with water (10 mL) was added to a warm solution of o- MAGPACK [40], was used to model the experimental phthalic acid (0.83 g, 5 mmol) and 4-MeIm (0.82 g, magnetic susceptibility data. 10 mmol) in water (30 mL). The resulting mixture was stirred and heated for 30 min. The blue microcrystalline precipitate was filtered off, washed with water and 3. Results and discussion ethanol and dried in air. Yield: 1.3 g, 64.2%. Anal. Calc. for C16H18CuN4O5: C, 46.88%; H, 4.43%; N, 13.67%. 3.1. Synthesis and preliminary characterization Found: C, 46.2%; H, 4.37%; N, 13.2%. IR data (KBr, cmÀ1): 3430s,br, 3145br, 3004sh, 1604sh, 1584sh, Reaction of metal(II) acetate with 4-MeIm and 1552vs,br, 1502s, 1489s, 1446sh, 1434s, 1407vs, 1396vs, KHPht or H2Pht in water in a 1:2:1 mole ratio 1261w, 1238w, 1160w, 1110s, 1088w, 971m, 852m, under heating leads to formation of polymers 3 Table 1 Crystal data and details of structural determinations 12 Empirical formula C16H18CoN4O5 C16H18CuN4O5 Formula weight 405.27 409.88 Temperature (K) 153(2) 153(2) Wavelength (A˚ ) 0.71073 0.71073 Crystal size (mm) 0.40 Â 0.40 Â 0.40 0.40 Â 0.20 Â 0.15 Crystal system Monoclinic Monoclinic Space group P21=nP21=n a (A˚ ) 11.4507(9) 11.6836(15) b (A˚ ) 9.1139(5) 9.0050(8) c (A˚ ) 16.3485(12) 16.504(2) b (deg) 100.178(6) 100.159(10) V (A˚ 3) 1679.3(2) 1709.2(3) Z 44 3 Dc (g/cm ) 1.603 1.593 m (mmÀ1) 1.059 1.314 F(000) 836 844 y range for data coll. (deg) 2.01–29.53 1.98–29.65 Index ranges À15php15, À14php16, À11pkp12, À12pkp10, À22plp22 À22plp22 Reflections measured 20538 20538 Independent reflections 4647 [R(int)=0.0494] 4647[R(int)=0.0494] Data/restraints/parameters 4647/0/300 4654/0/300 Goodness-of-fit on F2 1.051 1.005 Final R indices [I42sðIÞ] R1 ¼ 0:0284 R1 ¼ 0:04212 wR2 ¼ 0:0745 wR2 ¼ 0:0936 R indices (all data) R1 ¼ 0:0321 R1 ¼ 0:0673 wR2 ¼ 0:0763 wR2 ¼ 0:1042 Largest diff.